An image sensor provides a grid of pixels which may contain photosensitive diodes or photodiodes, reset transistors, source follower transistors, pinned layer photodiodes, and/or transfer transistors for recording intensity or brightness of light. The pixel responds to the light by accumulating photo-charges—the more light, the more the photo-charges. The charges can then be used by another circuit so that a color and brightness can be used for a suitable application, such as a digital camera. Common types of pixel grids include a charge-coupled device (CCD), a complimentary metal oxide semiconductor (CMOS) image sensor (CIS), an active-pixel sensor (APS), and a passive-pixel sensor.
In order to capture color information, image sensors employ a color filter layer that incorporates several different color filters (e.g., red, green, and blue), and are positioned such that the incident light is directed through the filter. This can be done by using organic-based color filter materials, such as polymer dye-based or pigment-based materials, to filter out specific frequency bands (colors). Either way, the cost of the color filters used in image sensors accounts for a large part of the total cost of the image sensor. Additionally, the color filter layer adds to the physical size of the device.
Therefore, improvements in color filter design and fabrication are desired to reduce the cost and size of image sensors.